Chocolate Pudding 101

My grandmother makes this every New Year's Eve and it's worth the year's wait. =)

Ingredients:
6T sugar
3T corn starch
1 1/2 T cocoa powder
pinch of salt
2 1/3 c. heavy cream, divided
1 1/4 c. milk (whole milk is best)
1 t. vanilla
6oz. semisweet chocolate, finely chopped
1 1/2 T unsalted butter, chopped into small pieces

1. In a medium saucepan, whisk together sugar, cornstarch, cocoa and salt. In a 4-cup measuring cup, combine 1 1/4 cup of the heavy cream with milk & vanilla. Whisk 1 cup cream mixture into dry ingredients until cornstarch is completely dissolved. Whisk in remaining cream mixture until smooth.
2. Place saucepan over medium heat. Cook, whisking constantly until mixture comes to a boil and thickens, about 4-5 minutes. Add chocolate and cook, whisking until chocolate is melted--about one minute. Remove from heat, and whisk in butter until melted. Using a 3oz. ladle, pour pudding into 6 dessert cups. Cool until completely set...about 1 hour.
3. Whip remaining cream to soft peaks. Serve with pudding.